The present invention is directed to a material-handling system and method of supplying work units in such a material-handling process. While the invention is illustrated for use in an order fulfillment system, it has other applications as well.
In a particular order fulfillment system, work units such as inventory receptacles, containing inventory items, are supplied to processing stations, such as goods-to-person stations for sorting by human operators into transport receptacles. The transport receptacles may represent individual orders or interim receptacles that are sent to further processing, such as at a put wall for organization into individual orders. The inventory receptacles are supplied under a warehouse management system from an inventory store, such as an automated warehouse system. An inventory receptacle transfer system transports the receptacles to a sorter which sorts inventory receptacles to the individual processing stations. The receptacles are allowed to accumulate at a buffer or accumulator at each processing station to allow individual operators to work at their own pace. However, when the buffer at a processing station cannot accept additional receptacles, the receptacles get recirculated in the sorter that supplies the receptacles to the processing stations. If enough receptacles are over-supplied, then the sorter gets filled with recirculation of receptacles intended for the slower operators thus preventing receptacles getting supplied to the faster operators who have an inadequate inventory receptacle at their station to process. Thus the system gets bogged down and must be operated at a slower pace to accommodate slower operators. Meanwhile the faster operators are idle.